Abstract: We present new observations of the early X-ray afterglows of the first 27
gamma-ray bursts (GRBs) detected with the Swift X-ray Telescope (XRT). The
early X-ray afterglows show a canonical behavior, where the light curve broadly
consists of three distinct power law segments: (i) an initial very steep decay
(t^{-alpha} with 3<alpha_1<5), followed by (ii) a very shallow decay
(0.2<alpha_2<0.8), and finally (iii) a somewhat steeper decay (1<alpha_3<1.5).
These power law segments are separated by two corresponding break times,
300s<t_{break,1}<500s and 10^3s<t_{break,2}<10^4s. On top of this canonical
behavior of the early X-ray light curve, many events have superimposed X-ray
flares, which are most likely caused by internal shocks due to long lasting
sporadic activity of the central engine, up to several hours after the GRB. We
find that the initial steep decay is consistent with it being the tail of the
prompt emission, from photons that are radiated at large angles relative to our
line of sight. The first break in the light curve (t_{break,1}) takes place
when the forward shock emission becomes dominant, with the intermediate shallow
flux decay (alpha_2) likely caused by the continuous energy injection into the
external shock. When this energy injection stops, a second break is then
observed in the light curve (t_{break,2}). This energy injection increases the
energy of the afterglow shock by at least a factor of f>4, and augments the
already severe requirements for the efficiency of the prompt gamma-ray
emission.